This invention relates to a technique for controlling communication in an electronic device system, including devices, such as an Audio Visual device (hereinafter, xe2x80x9cAV devicexe2x80x9d) that deals with visual information and audio information, and an information processing device, connected by a communication bus. Especially, the technique operates to prevent a use of the electronic device system that exceeds data the transfer capacity of the communication bus.
The IEEE 1394 serial bus is thought of as a network system that enables a transmission of data by isochronous communication and a transmission of a control signal by asynchronous communication between an AV device and an information processing device. The IEEE 1394 serial bus is standardized to xe2x80x9cIEEE STD 1394-1995xe2x80x9d as xe2x80x9cIEEE STANDARD FOR A HIGH PERFORMANCE SERIAL BUS.xe2x80x9d As an example of using IEEE 1394 serial buses, Japanese published unexamined patent application No. H08-47058 describes that xe2x80x9ca method for selecting input devicesxe2x80x9d that can display only the identification of a device that is able to output an information signal, as an input available device in a system that is connected to a plurality of electronic devices by way of a communication bus.
Further, an xe2x80x9cAV/C Digital Interface Command Setxe2x80x9d, which includes control signals to control an AV device for playback and recording of AV data by using a 1394 IEEE serial bus, has been opened to the public by the xe2x80x9c1394 Trade Association.xe2x80x9d However, in the standard technique for the IEEE 1394 serial bus, in case a plurality of electronic devices perform isochronous communication simultaneously, the available band width and number of channels of the bus are exceeded, and so some of the electronic devices that try to perform communication can not use the bus because of the short available band width and limited number of channels of the bus.
Consider a case wherein, in a network, for example, in which a digital receiver IRD (hereinafter xe2x80x9cIRDxe2x80x9d) is connected to a device such as a digital videotape recorder D-VTR (hereinafter xe2x80x9cD-VTRxe2x80x9d), a reserved recording is performed by the network. When the other electronic devices that are connected in the network use the bus during the reserved recording time, and the bus width that the IRD wants to use is larger than the available bus width at that time, the IRD cannot secure the necessary bus width. As a result, the reserved recording can not be performed because data can not be satisfactorily transmitted from the IRD to the D-VTR.
Further, in the input device selection method and AV/C Digital Interface Command Set, a method of selecting the input device at the present time, and a method of transmitting the data and the control signals at the present time are only considered.
The main object of the present invention is to solve the foregoing problems. In the case of an electronic device system in which an AV device and an information processing device are connected by a communication bus, and a reserved playback time and a reserved picture recording time are established, an inquiry is made of the connected devices to obtain information about each reservation. Then, on the basis of answer information received from the devices, it is determined how to perform a reservation for a communication resource, so that a usage that exceeds the transfer capacity of the communication bus is prevented, thereby allowing the reservation by the communication resource to be accepted.
Further, in accordance with this invention, in case a reservation or an immediate communication is impossible, the reason for this can be displayed. In addition, in case usage of a bus is prohibited because other devices have reserved the bus, the reason for this can be displayed.
This invention relates in particular to a system in which a device, such as AV device, is connected to an information processing device by a bus. In order to communicate in a reliable manner on the bus, a device that can perform data reproduction in the system inquires of the connected devices for reservation information. Responsive to an answer from the connected devices, the device has an element that can judge the availability of the bus transferring capacity not so as not to exceed the capacity of the bus. Therefore, a device that wants to use the bus can perform an information transfer. Further, by judging whether the above-mentioned usage of the bus is available, in a case where it is impossible to use the bus, the device has an element that communicates the reason to a video display device. Therefore, the device can perform an appropriate setting for the reservation to avoid problems in the use of the bus.